Apparatus for homogeneously combining finely divided substances



April 4,, 11950 FINELY DIVIDED SUBSTANCES Filed July 51, 1946 A y 1 F l; m s I. 4 moc 1 l a o 1 I J A I m .E I .my um a 2 8 &/ a m m n m 0 m d l fi\ m 9 r Patented Apr. 4, 1950 APPARATUS FOR HOMOGENEOUSLY COM- BINING FINELY DIVIDED SUBSTANCES Henry M. Collins, Vaughan Township, York County, Ontario, and Norman E. Adcock, Toronto, Ontario, Canada, assignors to Reliable Plastics Company, Limited, Toronto, Ontario,

Canada Application July 31, 1946, Serial No. 687,302

1 Claim.

This invention relates to a process for homogeneously combining finely divided substances by means of the injection of one finely divided substance entrained in a gas stream into a finely divided solid, and particularly means for the removal of the gas from the mixing vessel without entrainment of solid particles.

It is well known that finely divided powders may be rendered homogeneous by means of a tumbling process. Moreover, it is also known that any liquid which is compatible with one or more of these powders may be sprayed or aspirated into the powder charge at a relatively high rate of introduction, and the liquid will be completely absorbed into the powder particles. The most convenient, and usual method of introducing the compatible liquid is by forming a mist, or spray of the liquid, and injecting this spray into the powder mass in a jet of hot air or hot nitrogen.

Heretofore, the main difficulty has been to provide means for the escape of the injected air or nitrogen without allowing escape of the finely divided powder. Where fine screens or air permeable cloth have been used, it has been found that the dust particles invariably either pass through the filter, or clog the pores completely, stopping the process and possibly causing dangerous pressures in the tumbler.

Similarly where porous packings or composition plates have been used, blocking has invariably occurred. Where large enough inter stices have been provided to prevent blocking, considerable amounts of fine powder have been allowed to escape.

It is an object of the present invention to provide simple means for the escape of the gases introduced into an enclosure, casing or tumbler, without allowing appreciable escape of the finely divided substance therein.

We have found that by the use of a simple, novel, mechanical air filter, employing principles new to the art, a relatively large quantity of gas may be allowed to escape from the dust filled tumbler without an appreciable amount of the dust being expelled simultaneously.

By the use of this filtering means, finely divided powder can be agitated by means of a gaseous discharge, or dried by a gas stream, or liquids can be sprayed into an agitated powder charge, or any process involving the use of a gaseous fluid discharge into a mass of finely divided particles may be carried out without the danger of blocking the air outlet, and without losing an appreciable amount of the said powder charge.

One general embodiment of the present invention is described with reference to the accompanying drawings in which,

Figure 1 illustrates a partial sectional view of a tumbler comprising the present invention, and

Figure 2 shows an axial plan view of the arrangement of the filter parts as seen from plane 2-2 in Fig. 1 and reveals the section line of Figure 1.

Figure 3 illustrates a side view, on a reduced scale, of a tumbler comprising the present invention.

Figure 4 illustrates an enlarged sectional view of one of the double tubes used in the filter members.

Referring now more specifically to the drawings, in is a typical barrel-type tumbler, having fixed at either end massive bushings ll, rotatably mounted on the stationary hollow shaft l2. The tumbler l0 may be rotated about shaft 12 in any well known manner.

A series of double concentric tubes 13 lead from a source of air pressure, and a source of the liquid to be introduced to the tumbler, and terminate in spray jets or nozzles M which are of any variety known, such as used at present for producing a spray of finely divided droplets. In the tubes 13, the air may be passed through the annular space between the walls of the two tubes and the liquid may be passed through the central tube, or vice versa, depending on the type of nozzle used.

The fiow of the gaseous jet l5 of the mixture emanating from nozzles I4 is substantially conical in shape, and is controlled in this case by two conical shields l6 and I9, the larger of which, I6, is concentric with and pointing towards the exhaust port l8, and spaced from it by a single supporting member 11, which is so designed as to avoid any appreciable interference with the free flow of gases in all directions about the shield. The smaller shield 19 is concentric with, and pointing away from the exhaust port i8, and spaced from it by supports 20. The function of this smaller shield, in addition to helping to control the flow of the jets i5, is to deflect any particles entrained in the exhaust gas, and prevent their entry into the exhaust pipe 2|.

It is to be understood, however, that the design of shields l6 and I9 is not to be limited by the above disclosure. Obviously different shapes, sizes and arrangement of shields are necessary for difierent arrangements of jets l5.

In operation the jets cause formation of a shield of rapidly moving gas, directly over and about the exhaust port, so that any entrained solid particles in gas which is seeking to enter the exhaust port will be carried away, and re turned once more to the centre of the tumbler.

The efiiciency of the filtering action is best demonstrated with reference to the following example:

In a conventional brass tumbler of about 8 litres capacity, fitted with the mechanism described herein, was tumbled at 2'7 R. P. M. 600 grams of cellulose acetate flake of a particle size between 20 and 100 mesh. While tumbling, 300 grams of diethylphthalate was sprayed into the agitated powder mass at a rate of flow equal to 400 grams per hour by means of air heated to 350 degrees Fahrenheit and forced through a fine spray jet under 20 pounds pressure per square inch. After forty-five minutes, all the liquid plasticizer had been added. After one hour, the air was stopped and the resultant dry, freeflowing powder removed. Tests showed that the liquid was completely dispersed throughout each particle. Less than 0.1% of the powder charge was discharged through the exit tube of the main shaft; in no case was there any blocking of or cessation of exit air flow.

The above example demonstrates some of the advantages of the present invention over previously used methods, but is not intended in any way to narrow its scope.

It will be readily appreciated that the present invention has a wide application in fields other than those indicated, and could be used to advantage in any process where substances are to be homogeneously added to any finely divided powder, and where gases must be exhausted without loss of the powder. For the purpose of general example in this respect, the invention is applicable to the addition of liquid perfumes to talcum or face powder.

The composition of the jet which is introduced 4 from the nozzles obviously may be varied so that it includes one or more materials to be added to the powder charge, or on the other hand, only heated air or nitrogen for drying the powder. In short, without departing from the spirit of the invention, a gas, a mixture of gases, a mixture of gases and liquids, a mixture of gases and finely divided solid particles for the above purpose is obviously within its scope. It includes the addition of any suitable gaseous fluid.

What we claim as our invention is:

Apparatus for treatment of finely divided substances comprising a rotatable enclosure designed to enclose a charge of the finely divided substances, an exhaust port at one end of said enclosure aligned with the axis of rotation thereof, a plurality of injection nozzles arranged about said exhaust port equidistant from said axis and forming inlet ports for the introduction of gaseous fluid into said enclosure, said nozzles being thereby disposed to direct the injected gaseous fluid between the charge of finely divided substances and the exhaust port and around and about said exhaust port to substantially isolate the latter from said charge, whereby the injected gaseous fluid forms a filter in advance of and across said exhaust port.

HENRY M. COLLINS. NORMAN E. ADCOCK.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,198,595 Sharpe Aug. 29, 1916 2,292,897 Neilsen Aug. 11, 1942 2,306,962 Kropp Dec. 29, 1942 FOREIGN PATENTS Number Country Date 57,144 Denmark Jan. 15, 1940 

